Automotive cooling systems

ABSTRACT

An automotive heat exchange type cooling system includes an automotive radiator coupled with a reservoir exteriorly disposed thereof and vented to the atmosphere and a two-phase aqueous coolant, one phase being capable of forming a supernatant layer on the surface of the other when in the reservoir to retard evaporation thereof.

I Unlted States Patent 11 1 1111 3,809,152 Boehmer May 7, 1974 [5 AUTOMOTIVE COOLING SYSTEMS 2,768,955 10 1956 Heisigm; 252/78 2,951,038 8/1960 Holzinger 252/73 [75] Mfmhew Allen Park 3,238,136 3/1966 Willard etal..... 252/75 Mlch- 3,346,501 10/1967 Boehmer 252/73 AssigneeI wyandotte Cormrafion, 3,580,847 5/l97l Boehmer 252/75 Wyandotte, Mich. OTHER PUBLICATIONS [22] Filed; July 22, 1971 Pluronic Surfactants as Rinse Aids, Wyandotte Chemicals Corporation, F3305. l963. [2]] Appl. No.: 165,329

Related US. Application Data S' g S A g l k ssistant xaminerarris it ic [63] ggg g ss llg of Attorney, Agent, or Firm-Bernhard R. Swick;

Y Joseph D. Michaels; Robert E. Dunn [52] 11.8. C1 165/51, 252/73, 252/75,

252/358, 165/134, 123/4154 [571 ABSTRACT [51] Int. Cl C09n 3/02 An motive heat exchange type cooling system in- 58] Field of Search 252/73, 72, 74, 75, 76, cludes an automotive radiator coupled with a reservoir 252/77, 78, 358; 260/615; 165/51; 123/4154 exteriorly disposed thereof and vented to the atmosphere and a two-phase aqueous coolant, one phase [56] Refer e Cit d being capable of forming a supernatant layer on the UNITED STATES PATENTS surface of the other when in the reservoir to retard 2,462,694 2/1949 Walker 252/75 evaporanon thereof 2,751,355 6/1956 Clark 252/75 3 Claims, No Drawings AUTOMOTIVE COOLING SYSTEMS This application is a continuation-in-part of copending US. Pat. application Ser. No. 782,468, filed Dec. 9, 1968 and now abandoned.

With the development of new engine coolants, the trend in the automotive industry has been to recommend that the coolants be used throughout the year and thereafter for a period of several years instead of being replaced by water each summer.

Obviously, if a portion of the coolant is lost during auto operation and has to be replaced, the advantage of reduced service is dissipated. Consequently, a sealer is often added to the system upon assembly of the auto to aid in sealing off minor leaks. Barring a badly cracked block or head or a leaking head gasket, the sole remaining possibility for exit of the coolant from the system is the standard overflow tube or extension located in the radiator filler neck,

To prevent permanent loss of coolant past the pressure relief valve in the radiator cap and out the overflow tube, inventors heretofore have provided auxiliary reservoirs.

In one prior art system, return from the reservoir to the system proper of the coolant, which contracts as it and the engine cools, is accomplished by making use of the resulting vacuum which is normally relieved in a conventional system by air from the atmosphere moving through the overflow extension and past a vacuum relief valve located in the cap. The coolant, therefore, in response to the vacuum, flows by way of the overflow conduit from the reservoir, aided by the atmospheric pressure therein, back into the radiator through the overflow extension and through the open vacuum relief valve. A more complete description of such sealed cooling system is found in Automotive News, Oct. 21, 1968, pages and 21.

While in this system the radiator and coolant system itself is sealed, the overflow or reservoir is not since there must be communication between the outside atmosphere and the reservoir in order for the atmo spheric pressure to force the fluid back into the radiator. Since the reservoir presents a fairly large liquid surface which for all effects and purposes is open to the atmosphere, the coolant liquid, which is generally at an elevated temperature, normally evaporates from this surface. This loss by evaporation over a period of time could become serious and eventually enough water or other liquid component could be lost whereby when the fluid is forced back into the radiator byatmospheric pressure there would be insufficient fluid to fill the reservoir and air would then enter the radiator.

Thus, an advancement in the art would be provided by a cooling system of the type herein described wherein the problems presented by evaporation of water or similar coolants in the auxiliary tank or reservoir are eliminated or substantially reduced.

In accordance with this invention, an automotive heat exchange cooling system comprises a radiator, an overflow tube or conduit, an atmospheric pressureequilibrated reservoir and a two-phase liquid composition consisting essentially of (A) an aqueous coolant liquid of the type conventionally employed in heatexchange type cooling systems for internal combustion engines as a first phase and (B) a liquid having a specific gravity less than that of the coolant liquid (A) as a second phase which is immiscible with the coolant liquid (A), is substantially non-evaporative, is relatively impermeable to vapors from the coolant liquid (A);

and forms a supernatant layer floating on the surface of coolant liquid (A) when in the reservoir. It is preferred that the two-phase coolant composition of this invention consist essentially of about to 99.9 percent by weight of the aqueous coolant liquid (A) and 0.1 to 5 percent by weight of the floating liquid (B).

The coolant liquid (A) is a conventional liquid coolant for use in heat-exchange type cooling systems for internal combustion engines. Such coolants generally comprise water and a glycol type freezing point depressant. It is preferred to employ water-soluble polyhydric alcohols or ethers as freezing point depressants. These may be any of the common glycols or glycol ethers having about 2 to about 14 carbon atoms such as ethylene glycol, diethylene glycol, triethylene glycol, prop ylene glycol, dipropylene glycol, ethylene glycol ethers such as the ethyl, methyl, propyl, and butyl ethers thereof and similar ethers of diethylene and triethylene glycol and mixtures thereof. ln general, it is preferred to use the simpler compounds as represented by the polyhydric alcohols such as ethylene glycol, propylene glycol, butylene glycol, glycerine, and diethylene glycol for they are easily obtainable and blend easily with water to give very low freezing mixtures suitable for use in automobile cooling systems. The amount of freezing point depressant employed depends on the temperatures to which the coolant liquid (A) will be subjected.

in addition to the polyhydric alcohol, such coolant liquids generally also include various agents to lessen the tendency of such solutions to become corrosive to the metals in the cooling system. Among the corrosion inhibitors that have been used and which may be used are borax, triethanolamine, sulfonated oils, resinates, sodium nitrite, sodium benzoate, triethanol ammonium phosphate, mercaptobenzothiazole, sodium mercaptobenzothiazole and other alkali metal mercaptobenzothiazoles, alkali metal orthophosphates, molybdates, tungstates, urea, naphthenates, etc., which are used either alone or in combination.

The floating liquid (B) may consist of any organic liquid which (1 does not interfere with normal coolant liquid function, (2) has a lower specif c gravity than the coolant liquid (A), (3) is substantially non-evaporative, (4) spreads to form a supernatant layer over the surface of the coolant liquid (A), (5) is relatively impermeable to vapors from the coolant liquid (A), (6) is immiscible with the coolant liquid (A), (7) is nonfoaming, and (8) is non-corrosive in both liquid and vapor phase.

The immiscible floating liquid (B) particularly adaptedfor use herein, is a cogeneric mixture of conjugated polyoxyalkylene compounds containing in their structure at least one hydrophobic oxyalkylene chain in which the oxygen/carbon atom ratio does not exceed- 0.40 and at least one hydrophilic oxyalkylene chain in which the oxygen/carbon atom ratio is greater than 0.40. In accordance with the preferred practice of this invention, the hydrophilic oxyalkylene chain is less than 20 percent of the total weight of the oxyalkylene chain.

Polymers of oxyalkylene groups obtained frompropylene oxide, butylene oxide, amylene oxide, styrene oxide, mixtures of such oxyalkylene groups with each other and with minor amounts of polyoxyalkylene groups obtained from ethylene oxide, butadiene dioxide, and glycidol are illustrative of hydrophobic oxyalkylene chains having an oxygen/carbon atom ratio not exceeding 0.40. Polymers of oxyalkylene groups obtained from ethylene oxide. butadiene dioxide. glycidol, mixtures of such oxyalkylene groups with each other and with minor amounts of oxyalkylene groups obtained from propylene oxide. butylene oxide. amylene oxide and styrene oxide are illustrative of hydrophilic oxyalkylene chains having an oxygen/carbon atom ratio greater than 0.40.

Among the conjugated polyoxyalkylene compounds which can be used in the system of the invention are those which correspond to the formula:

wherein Y is the residue of organic compound having from about one to six carbon atoms and one reactive hydrogen atoms. n has an average value of at least 6.4 as determined by hydroxyl number and m has a value such that the oxyethylene portion constitutes up to about 20 weight percent of the molecule. These surface active agents are more particularly described in U.S. Pat. No. 2.677.700.

Other conjugated polyoxyalkylene compositions which are most advantageously used in the present heat exchange system is floating liquid (B) correspond to the formula:

herein 1 is the residue of an organic compound having from about two to six carbon atoms and containing x reactive hydrogen atoms in which x has a value of at least about 2. n has a value such that the molecular weight of the polyoxypropylene hydrophobic base is at least about 900 and m has a value such that the oxyethylenc content of the molecule is up to about 20 weight percent. Compounds falling within the scope of the definition for 1 include. for example. propylene glycol. glycerine. pentaerythritol. trimethylolpropane. ethylene diamine. and the like. As already noted. the oxypropylene chains optionally. but advantageously. contain small amounts of ethylene oxide and the oxyethylene chains also optionally. but advantageously. contain small amounts of other alkylene oxides such as propylene oxide and butylene oxide. These compositions are more particularly described in U.S. Pat. No. 2.674.619. These polyoxyalkylene compositions include the nitrogen containing polyoxyalkylene compounds of U.S. Pat. No. 2.979.528. Suitable polyoxyalkylene compounds are also disclosed in US. Pat. No. 2.425.755.

The preferred floating liquid (B) consists of the cogeneric mixtures of the polyoxyalkylene copolymers of ethylene oxide and propylene oxide which may be block or heteric in type or mixtures thereof, containing to percent by weight ethylene'oxide units and 100 to 85 percent propylene oxide units having molecular weights of from about 1.200 to 5.000. Such compositions are hydrophobic in nature due to the predominance of the propylene oxide units.

The floating liquid (B) may also include a vapor phase corrosion inhibitor which may consist of any of the common vapor phase corrosion inhibitors such as amines, acids, amine-acid complexes. and other materials commonly known to those skilled in the art. Conventional vapor phase corrosion inhibitors include morpholine, dibutylamine. and cyclohexylamine and combinations of them may be employed. Such inhibitors are disclosed by Baker in Volatile Rust lnhibitors," Industrial and Engineering Chemistry. Vol. 46. December 1954. page 2592.

The range of proportions of the components of the composition of this invention may vary widely. For example, good results are obtained with a composition which consists essentially of the above-described aqueous coolant liquid (A) which comprises by weight about 15 to 60 percent dihydroxy aliphatic alcohol, 0.02 to 5.0 percent of at least one corrosion inhibitor, about 0.0005 to 0.3 percent of at least one antifoaming agent. and about 0.01 to 3.0 percent of at least one buffering agent to maintain alkalinity and an immiscible floating liquid (B), as above described, containing from 50 to percent by weight of at least one of the polyoxyalkylene compounds and from 0 to 50 percent by weight of at least one vapor phase corrosion inhibitor.

The practice of this invention will be more completely understood by reference to the following examples.

EXAMPLE A coolant fluid (A) was prepared which consisted of a 1:1 mixture by weight of ethylene glycol and water containing 0.5 percent sodium tetraborate pentahydrate, 0.1 percent sodium hydroxide, 0.2 percent trisodium phosphate dodecahydrate, 0.15 percent sodium mercaptobenzothiazole, 0.05 percent sodium metasilicate, and about 0.125 gram per gallon of a rose dye.

500-milliliter portions of the above solution were placed in each of nine 1,000-milliliter pyrex glass beakers fitted with a rubber stopper containing a inch diameter hole and a liquid (B) added to six of the beakers. The liquid (B) in each case was a cogencric mixture of polyoxyethylene-polyoxypropylenepolyoxyethylene block copolymers having an average molecular weight of the polyoxypropylene base of about 1,750 and a polyoxyethylene content of the molecule of about 10 weight percent. Liquid (B) floated on the top of the coolant with the thickness being A; inch in three beakers, A inch in three beakers leaving three beakers with no floating liquid (B). The beakers were stoppered and weighed to the nearest gram. The beakers and contents were stored for several days at the various temperatures set forth in the Table below and periodically weighed to determine the weight loss due to evaporation. Natural convection ovens were employed as the storage chambers.

The periodic weight losses for each beaker were averaged to determine the amount of weight loss per day of test and the data obtained was transposed to values of loss in grams per 25 square inches of liquid surface per day to be more relevant to the size of reservoir normally in use in a vehicle engine.

TABLE Average Weight Losses in Grams Per 25 Square lnchcs Per Day La'yer Thickness Solution Temperature. F. 220

Inches I90 0 15 gms. 23 gms. 582 gms. Va 1 ll 96 V4 (1 5 78 completely eliminated evaporation loss at a temperature of 125 E.

While there has been shown and described hereinabove the present preferred embodiments of this invention, it is to be understood that various changes, alterations and modifications can be made thereto without departing from the spirit and scope thereof as defined in the appended claims.

What is claimed is:

1. In an automotive heat exchange cooling system comprising a radiator, an overflow tube having one end thereof operatively coupled with the radiator, and a reservoir disposed exteriorly from the radiator operatively connected to the other end of the tube, the reservoir being vented to the atmosphere to equilibrate the pressure in the system, the improvement which comprises using as the heat exchange medium a two-phase circulating fluid composition therefor consisting of:

A. an aqueous dihydric alcohol or ether thereof, base coolant liquid selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol. propylene glycol, dipropylene glycol, and methyl, ethyl, propyl and butyl ethers of ethylene, diethylene, and triethylene glycols, and

B. a liquid cogeneric mixture of conjugated polyoxyalkylene compounds having molecular weights of from about 1,200 to 5,000 which compounds contain in their structure at least one hydrophobic oxyalkylene chain in which the oxygen/carbon atom ratio does not exceed 0.40 and at least one hydrophilic oxyalkylene chain in which the oxygen/carbon atom ratio is greater than 0.40 wherein the hydrophilic oxyalkylene chain is less than 20 percent of the total weight of the oxyalkylene chain, wherein the amount of phase (B) floating onitop of phase (A) has a minimum liquid thickness of about /8 inch when in the reservoir to prevent evaporation of phase (A) and is present in an amount of up to 5 percent by weight of the total composition. 2. The system of claim 1 wherein said liquid (B) is a cogeneric mixture of block or heteric type polyoxyalkylene copolymers of ethylene oxide and propylene oxide containing 0 to 15 percent by weight ethylene oxide units and 100 to percent propylene oxide units having molecular weights of from about 1,200 to 5,000.

3. The system of claim 2 wherein said liquid (A) comprises by weight about 15 to 60 percent dihydroxy aliphatic alcohol, about 0.02 to 5.0 percent of at least one corrosion inhibitor, about 0.0005 to 0.3 percent of at least one antifoaming agent, about 0.0l to 3.0 percent of at least one buffering agent to maintain alkalinity, and the balance water. 

1. In an automotive heat exchange cooling system comprising a radiator, an overflow tube having one end thereof operatively coupled with the radiator, and a reservoir disposed exteriorly from the radiator operatively connected to the other end of the tube, the reservoir being vented to the atmosphere to equilibrate the pressure in the system, the improvement which comprises using as the heat exchange medium a two-phase circulating fluid composition therefor consisting oF: A. an aqueous dihydric alcohol or ether thereof, base coolant liquid selected from the group consisting of ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, and methyl, ethyl, propyl and butyl ethers of ethylene, diethylene, and triethylene glycols, and B. a liquid cogeneric mixture of conjugated polyoxyalkylene compounds having molecular weights of from about 1,200 to 5,000 which compounds contain in their structure at least one hydrophobic oxyalkylene chain in which the oxygen/carbon atom ratio does not exceed 0.40 and at least one hydrophilic oxyalkylene chain in which the oxygen/carbon atom ratio is greater than 0.40 wherein the hydrophilic oxyalkylene chain is less than 20 percent of the total weight of the oxyalkylene chain, wherein the amount of phase (B) floating on top of phase (A) has a minimum liquid thickness of about 1/8 inch when in the reservoir to prevent evaporation of phase (A) and is present in an amount of up to 5 percent by weight of the total composition.
 2. The system of claim 1 wherein said liquid (B) is a cogeneric mixture of block or heteric type polyoxyalkylene copolymers of ethylene oxide and propylene oxide containing 0 to 15 percent by weight ethylene oxide units and 100 to 85 percent propylene oxide units having molecular weights of from about 1,200 to 5,000.
 3. The system of claim 2 wherein said liquid (A) comprises by weight about 15 to 60 percent dihydroxy aliphatic alcohol, about 0.02 to 5.0 percent of at least one corrosion inhibitor, about 0.0005 to 0.3 percent of at least one antifoaming agent, about 0.01 to 3.0 percent of at least one buffering agent to maintain alkalinity, and the balance water. 